Es had been estimated using a model for the calculation from the particle film growth price primarily based around the thermo phoretic velocity previously created [52,53] and found to be 100 25 nm for Sample #1 and 200 25 nm for Sample #2. Within this study, the process as well as the total sampling instances had been selected to make thick nanoparticle films covering the whole substrate, so avoiding any interaction be tween the AFM tip as well as the mica LAU159 References muscovite substrate that may well impact the nanoindentation measurement from the samples. Additionally, for PEN, HOPG and soot particle films the area indented by an indenter of 5000 nm radius may be viewed as as a semiinfinite space and so the hardness and Young’s modulus values could be assumed to become right. On the other hand, that is not achievable for any single particle having a dimension Remacemide supplier inside the similar order of magnitude from the tip radius, and even lower [21]. Moreover, the imaging of a nanoindent performed on a single nanoparticle is pretty hard to carry out. It can be worth underlining that nanoindentation measurements on single soot particles have been performed and re ported, but for the reasons listed above they couldn’t be taken with full self-confidence on an absolute scale [21].Appl. Sci. 2021, 11,7 ofFigure four reports typical force istance curves measured on Sample #1 and on Sample #2. It is possible to observe that at a provided deformation the maximum load applied to Sample #2 is higher than that of Sample #1. The adhesion forces measured for both sam ples are within the order of 0.2 0.01 N.Figure four. Force istance curves measured through approach (green line) and retract (red line) on Sample #1 (a) and on Sample #2 (b).Figures five and 6 show semicontact AFM pictures of an indent on Sample #1 surface (Figure 5a) and Sample #2 surface (Figure 6a), too because the exact same pictures analyzed with the Gwyddion computer software and marked using a red mask made use of to calculate the projected area (Figures 5b and 6b). The projected regions in the intend resulted in AP 10000 500 nm2 for Sample #1 and AP 11000 500 nm2 for Sample #2.Figure five. Semicontact AFM image of an indent on Sample #1 surface (a); identical image as in the upper panel just after cropping and evaluation using the application Gwyddion (b).Appl. Sci. 2021, 11,eight ofFigure 6. Semicontact AFM image of an indent on Sample #2 surface (a); same image as inside the upper panel after cropping and evaluation with all the software Gwyddion (b).The results of nanoindentation measurements are reported in Table 2. The mean val ues of hardness measured from the maximum load plus the intend region have been H = 0.75 0.05 GPa for Sample #1 and H = 0.9 0.05 GPa for Sample #2. The analysis with the retraction curves with the DMT match model reported a mean Young’s modulus E = four.2 0.3 GPa for Sample #1 and E = 7.2 0.4 GPa for Sample #2. Exactly the same Poisson ratiosample = 0.three as for HOPG was made use of.Table 2. Hardness and Young’s modulus measured by AFM nanoindentation on Sample #1 and Sample #2 and in comparison to PEN and HOPG. Errors are reported as the mean typical deviation from 20 independent measurements.Sample Sample #1 Sample #2 PEN HOPGHardness H, GPa 0.75 0.05 0.90 0.05 0.70 0.05 two.40 0.Young’s Modulus E, GPa 4.2 0.3 7.2 0.four three.eight 0.3 7.5 0.Both Sample #1 and Sample #2 films showed lower hardness and Young’s modulus compared to HOPG. This may very well be explained taking a look at the structure of particle films. Soot nanostructured films are composed by nanoscale grains which can be deemed because the standard.